During the preparation of integrated circuit modules, an encapsulating or potting composition such as an epoxy formulation is applied to hermetically seal the backside of the module. During the curing of the potting composition, unwanted residue therefrom is deposited on the input/output (I/O) pins of the module. This residue if not adequately removed can cause poor electrical conductivity which can render the electrical connections into, for instance, a printed circuit board somewhat unreliable. Prior to the present invention, it has been necessary to either scrub or burn the pins in order to remove as much as possible of the residue. Scrubbing, however, can physically damage the pins. Also, the closer pins are located to each other on a chip or module, the more difficult it is to get between them for scrubbing. Burning, on the other hand, is not entirely satisfactory since it exposes the device to excessive heat which can adversely affect the performance of the device.
Accordingly, it is an object of the present invention to provide means which significantly reduces if not completely eliminates residue from tenaciously adhering to the pins, and which greatly facilitates the removal thereof. The present invention offers the advantage that only a simple washing is needed after the backseal operation to clean the pins.
When the module is to be connected to a printed circuit board by a soldering process, flux compositions have been applied to the pins. Flux compositions are employed to remove oxides from the pins and to prevent the pins from oxidizing when subjected to elevated temperature thereby serving to maintain the electrical conductivity of the pins. It has been found, according to the present invention, that the compositions which have been found by applicants to be suitable for preventing the build-up of residue on the pins during the backsealing operation also can function as a fluxing composition.
Although numerous flux compositions have been suggested in the prior art, applicants are not aware of any such compositions which have also been employed on a commercial basis to act as a temporary protective coating on conductive pins to prevent the formation of tenacious residue due to the backsealing operation.